Neuromonitoring systems and methods for bone fixation or fusion procedures

ABSTRACT

A surgical procedure to insert an implant into the body of a patient may impinge upon or run the risk of damaging neural tissue during the insertion procedure. To reduce this risk, the implant and instrumentation used during the implantation procedure can be modified or adapted for use as neuromonitoring probes to determine whether a nerve is in close proximity.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/141,666, filed Apr. 1, 2015, titled “NEUROMONITORING SYSTEMS AND METHODS FOR BONE FIXATION OR FUSION PROCEDURES,” which is herein incorporated by reference in its entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

FIELD

Embodiment of the invention relate generally to neuromonitoring systems, devices and methods, and more specifically to neuromonitoring systems, devices and methods for bone fixation or fusion procedures.

BACKGROUND

Many types of hardware are available both for the fixation of bones that are fractured and for the fixation of bones that are to be fused (arthrodesed).

For example, the human pelvic girdle (see FIGS. 1 and 2) is made up of three large bones joined together by three relatively immobile joints. One of the bones is called the sacrum and it lies at the bottom of the lumbar spine, where it connects with the L5 vertebra. The other two bones are commonly called “pelvic bones” and are technically referred to as the right ilium and-the left ilium. The sacrum connects with both pelvic bones at the sacroiliac joint (in shorthand, the SI-Joint).

The SI-Joint functions to transfer forces from the spine to the lower extremities, and vice-versa. The SI-Joint has been identified as the pain generator in up to 22% of patients who present with lower back pain.

Sacroiliac joint fusion is a surgical procedure that is performed to alleviate pain coming from the SI joint in patients who have failed to receive adequate pain relief with non-surgical treatments of the SI joint. Some conditions of the SI joint that may be treated with SI joint fusion (arthrodesis) are: degenerative sacroiliitis, inflammatory sacroiliitis, iatrogenic instability of the sacroiliac joint, osteitis condensans ilii, or traumatic fracture dislocation of the pelvis. Currently, screws and screws with plates are used as the standard instrumentation for sacro-iliac fusion. Historically, an SI joint fusion consisted of an open surgical approach to the SI joint from an anterior, a posterior, or a lateral direction. The surgeon would then debride (remove) the cartilage from the articular portion of the joint and the interosseous ligament from the fibrous portion of the joint. These open approaches require a large incision and deep soft tissue dissection to approach the damaged, subluxed, dislocated, fractured, or degenerative SI joint.

A typical technique for placing implants involves placement of one or multiple implants from a lateral to medial direction across the SI-Joint. These implants are placed with a starting point on the lateral aspect of the ilium. The implants are then directed across the ilium, across the sacroiliac joint and into the sacrum. Regarding implant position, care is taken to avoid impinging on neural structures, including neural tissue within the neural foraminae or spinal canal.

Accordingly, it would desirable to provide to provide systems and methods for determining the position and location of neural tissues proximate the implantation site.

SUMMARY OF THE DISCLOSURE

The present inventions relate generally to neuromonitoring systems, devices and methods, and more specifically to neuromonitoring systems, devices and methods for bone fixation or fusion procedures.

In some embodiments, a neuromonitoring system is provided. The neuromonitoring system can include a guide pin having a proximal end, a distal end, and an elongate body made of a conductive material; a guide pin adaptor configured to be secured to the proximal end of the guide pin; a signal generator in electrical communication with the guide pin adaptor; one or more recording electrodes configured to detect a electrophysiological signal from a patient; and a computing device in communication with the one or more recording electrodes, the computing device programmed to process the electrophysiological signal detected by the one or more recording electrodes.

In some embodiments, the neuromonitoring system further includes an electrically insulating sleeve covering a middle portion of the elongate body, leaving the proximal end and the distal end of the guide pin exposed.

In some embodiments, the guide pin adaptor comprises a receptacle for receiving the proximal end of the guide pin, the receptacle having an electrical contact.

In some embodiments, the electrical contact is selected from the group consisting of a leaf spring, an electrical brush, and a ball plunger.

In some embodiments, the electrical contact is a collar with one or more ball plungers, and the proximal end of the guide pin comprises a groove configured to receive the one or more ball plungers.

In some embodiments, the electrical contact is a clip configured to grasp the proximal end of the guide pin.

In some embodiments, a cannula for receiving a guide pin and electrically connecting the guide pin to a signal generator is provided. The cannula can include an elongate body have a proximal end, a distal end, and a lumen extending therethrough along a longitudinal axis of the elongate body; and one or more electrical contacts disposed on a proximal portion of the elongate body, the electrical contacts configured to electrically connect the guide pin to the signal generator when the guide pin is disposed within the lumen of the elongate body.

In some embodiments, the electrical contact is a removable insert.

In some embodiments, the electrical contact is a leaf spring.

In some embodiments, the elongate body is made from an electrically insulating material.

In some embodiments, the cannula further includes an electrically insulating liner disposed within the length of the lumen.

In some embodiments, the one or more electrical contacts are disposed within a proximal portion of the lumen.

In some embodiments, the one or more electrical contacts extend proximally from the proximal end of the elongate body.

In some embodiments, the one or more electrical contacts are biased towards the longitudinal axis.

In some embodiments, an impactor for advancing an implant into a bore and electrically connecting the implant to a signal generator is provided. The impactor can include an elongate body having a proximal end, a distal end, a longitudinal axis, wherein the distal end of the elongate body comprises an electrically insulated tip and one or more electrical contacts disposed on an implant contacting face of the distal end, wherein the one or more electrical contacts are configured to electrically connect the implant to the signal generator.

In some embodiments, the elongate body has a cross-sectional profile transverse to the longitudinal axis that matches a cross-sectional profile of the implant.

In some embodiments, the impactor further includes wires extending from the one or more electrical contacts to the proximal end of the elongate body.

In some embodiments, the impactor further includes a lumen extending the length of the elongate body.

In some embodiments, a system for advancing an implant into a bore and electrically connecting the implant to a signal generator is provided. The system can include an impactor comprising an elongate body having a proximal end, a distal end, a longitudinal axis, wherein the distal end of the elongate body comprises an electrically insulated tip and one or more electrical contacts disposed on an implant contacting face of the distal end, wherein the one or more electrical contacts are configured to electrically connect the implant to the signal generator; and a soft tissue protector comprising a lumen for receiving the impactor, wherein the lumen of the soft tissue protector is defined by an electrically insulating material.

In some embodiments, the lumen of the soft tissue protector has a cross-sectional profile that matches a cross-sectional profile of the impactor.

In some embodiments, the cross-sectional profile of both the lumen of the soft tissue protector and the impactor are substantially rectilinear.

In some embodiments, the cross-sectional profile of both the lumen of the soft tissue protector and the impactor are defined by one or more apices.

In some embodiments, a soft tissue protector for electrically connecting an implant to a signal generator is provided. The soft tissue protector can include an elongate body having proximal end, a distal end, a longitudinal axis, and a lumen extending from the proximal end to the distal end, the lumen defined by one or more electrically insulated walls and sized and shaped to receive the implant; and an electrical contact disposed on the distal end of the elongate body, the electrical contact configured to electrically connect the implant to the signal generator.

In some embodiments, the electrical contact extends distally from the distal end of the elongate body and is biased towards the longitudinal axis of the elongate body.

In some embodiments, the electrical contact is a leaf spring disposed within the lumen of the elongate body.

In some embodiments, the electrical contact is an insert that can be removably attached to the distal end of the elongate body.

In some embodiments, the soft tissue protector further includes a wire extending from the electrical contact to the proximal end of the elongate body.

In some embodiments, an implant checking device for electrically connecting an implant to a signal generator is provided. The implant checking device can include an elongate body having a proximal end, a distal end, a longitudinal axis, and a lumen extending from the proximal end to the distal end; an extendable and retractable probe disposed within the lumen of the elongate body, the probe having an extended configuration that is biased away from the longitudinal axis of the elongate body, wherein the probe in the extended configuration is configured to electrically connect the implant to the signal generator.

In some embodiments, the extendable and retractable probe is spring actuated.

In some embodiments, the extendable and retractable probe has a distal end that terminates in a ball.

In some embodiments, a method of inserting an implant into a patient is provided. The method can include inserting a guide pin into the patient at a first site; delivering a first electrical stimulus through the guide pin while the guide pin is inserted into the patient at the first site; monitoring a second site for a first electrophysiological signal after the step of delivering the first electrical stimulus; drilling a bore over the guide pin at the first site with a drill bit; shaping the bore with a broach; and inserting the implant into the bore.

In some embodiments, the method further includes delivering a second electrical stimulus through the drill bit; and monitoring the second site for a second electrophysiological signal after the step of delivering the second electrical stimulus.

In some embodiments, the method further includes delivering a second electrical stimulus through the broach; and monitoring the second site for a second electrophysiological signal after the step of delivering the second electrical stimulus.

In some embodiments, the method further includes delivering a second electrical stimulus through the implant; and monitoring the second site for a second electrophysiological signal after the step of delivering the second electrical stimulus.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

FIG. 1 illustrates an embodiment of an implant structure.

FIGS. 2A-2D are side section views of the formation of a broached bore in bone according to one embodiment of the invention.

FIGS. 2E and 2F illustrate the assembly of a soft tissue protector system for placement over a guide wire.

FIGS. 3 and 4 are, respectively, anterior and posterior anatomic views of the human hip girdle comprising the sacrum and the hip bones (the right ilium, and the left ilium), the sacrum being connected with both hip bones at the sacroiliac joint (in shorthand, the SI-Joint).

FIGS. 5 to 7A and 7B are anatomic views showing, respectively, a pre-implanted perspective, implanted perspective, implanted anterior view, and implanted cranio-caudal section view, the implantation of three implant structures for the fixation of the SI-Joint using a lateral approach through the ilium, the SI-Joint, and into the sacrum.

FIG. 8A is an anatomic anterior and lateral view of a human spine.

FIG. 8B is an anatomic posterior perspective view of the lumbar region of a human spine, showing lumbar vertebrae L2 to L5 and the sacral vertebrae.

FIG. 8C is an anatomic anterior perspective view of the lumbar region of a human spine, showing lumbar vertebrae L2 to L5 and the sacral vertebrae.

FIG. 9 is an anatomic anterior perspective view showing, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures as shown in FIG. 1, sized and configured to achieve anterior lumbar interbody fusion, in a non-invasive manner and without removal of the intervertebral disc.

FIG. 10 is an anatomic anterior perspective view showing the assembly shown in FIG. 9 after implantation.

FIG. 11 is an anatomic right lateral perspective view showing the assembly shown in FIG. 9 after implantation.

FIG. 12 is an anatomic superior left lateral perspective view showing the assembly shown in FIG. 9 after implantation.

FIGS. 13A to 13G are diagrammatic views showing, for purposes of illustration, a representative lateral (or posterolateral) procedure for implanting the assembly of implant structures shown in FIGS. 10 to 12.

FIG. 14 is an anatomic anterior perspective view showing, in an exploded view prior to implantation, assemblies comprising one or more implant structures like that shown in FIG. 1 inserted from left and/or right anterolateral regions of a given lumbar vertebra, in an angled path through the intervertebral disc and into an opposite anterolateral interior region of the next inferior lumbar vertebra, FIG. 14 showing in particular two implant structures entering on the right anterolateral side of L4, through the intervertebral disc and into the left anterolateral region of L5, and one implant structure entering on the left anterolateral side of L4, through the intervertebral disc and into the right anterolateral region of L5, the left and right implant structures crossing each other in transit through the intervertebral disc.

FIG. 15 is an anatomic anterior perspective view showing, in an exploded view prior to implantation, assemblies comprising one or more implant structures like that shown in FIG. 1 inserted from left and/or right anterolateral regions of a given lumbar vertebra, in an angled path through the intervertebral disc and into an opposite anterolateral interior region of the next inferior lumbar vertebra, FIG. 15 showing in particular one implant structure entering on the right anterolateral side of L4, through the intervertebral disc and into the left anterolateral region of L5, and one implant structure entering on the left anterolateral side of L4, through the intervertebral disc and into the right anterolateral region of L5, the left and right implant structures crossing each other in transit through the intervertebral disc.

FIG. 16 is an anatomic posterior perspective view, exploded prior to implantation, of a representative configuration of an assembly of one or more implant structures like that shown in FIG. 1, sized and configured to achieve translaminar lumbar fusion in a non-invasive manner and without removal of the intervertebral disc.

FIG. 17 is an anatomic inferior transverse plane view showing the assembly shown in FIG. 16 after implantation.

FIG. 18 is an anatomic posterior perspective view, exploded prior to implantation, of a representative configuration of an assembly of one or more implant structures like that shown in FIG. 1, sized and configured to achieve lumbar facet fusion, in a non-invasive manner and without removal of the intervertebral disc.

FIG. 19 is an anatomic inferior transverse plane view showing the assembly shown in FIG. 18 after implantation.

FIG. 20 is an anatomic lateral view showing the assembly shown in FIG. 18 after implantation.

FIG. 21A is an anatomic anterior perspective view showing, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures like that shown in FIG. 1, sized and configured to achieve fusion between lumbar vertebra L5 and sacral vertebra S1, in a non-invasive manner and without removal of the intervertebral disc, using an anterior approach.

FIG. 21B is an anatomic anterior perspective view showing the assembly shown in FIG. 21A after implantation.

FIG. 22A is an anatomic posterior view showing, in an exploded view prior to implantation, another representative configuration of an assembly of one or more implant structures 20 sized and configured to achieve fusion between lumbar vertebra L5 and sacral vertebra S1, in a non-invasive manner and without removal of the intervertebral disc, using a postero-lateral approach entering from the posterior iliac spine of the ilium, angling through the SI-Joint, and terminating in the lumbar vertebra L5.

FIG. 22B is an anatomic posterior view showing the assembly shown in FIG. 22A after implantation.

FIG. 22C is an anatomic superior view showing the assembly shown in FIG. 22B.

FIG. 23 is an anatomic lateral view showing a spondylolisthesis at the L5/S1 articulation, in which the lumbar vertebra L5 is displaced forward (anterior) of the sacral vertebra S1.

FIG. 24A is an anatomic anterior perspective view showing, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures like that shown in FIG. 1, sized and configured to stabilize a spondylolisthesis at the L5/S1 articulation.

FIG. 24B is an anatomic anterior perspective view showing the assembly shown in FIG. 24A after implantation.

FIG. 24C is an anatomic lateral view showing the assembly shown in FIG. 24B.

FIG. 25A illustrates an embodiment of a neuromonitoring system with a guide pin converted into a neuromonitoring probe using an adapter.

FIGS. 25B-25I illustrate various embodiments of guide pin adapters.

FIGS. 26A-26D illustrate various embodiments of guide pin cannulas that have been modified to convert a guide pin to a neuromonitoring probe.

FIGS. 27A-27C illustrate an embodiment of a modified impactor that converts an implant into a neuromonitoring probe.

FIGS. 28A-28D illustrate various embodiments of soft tissue protectors modified to convert implants and/or broaches into neuromonitoring probes.

FIG. 29 is an embodiment of a modified drill bit that can be used as a neuromonitoring probe.

FIG. 30 is an embodiment of a modified broach that can be used as a neuromonitoring probe.

FIGS. 31A and 31B illustrate embodiments of an implant checking device that can be used to determine whether an implant is close to neural tissue.

FIGS. 32A-32C illustrate the innervation of the body.

DETAILED DESCRIPTION

Elongated, stem-like implant structures 20 like that shown in FIG. 1 make possible the fixation of the SI-Joint (shown in anterior and posterior views, respectively, in FIGS. 3 and 4) in a minimally invasive manner. These implant structures 20 can be effectively implanted through the use a lateral surgical approach. The procedure is desirably aided by conventional lateral, inlet, and outlet visualization techniques, e.g., using X-ray image intensifiers such as a C-arms or fluoroscopes to produce a live image feed, which is displayed on a TV screen.

In one embodiment of a lateral approach (see FIGS. 5, 6, and 7A/B), one or more implant structures 20 are introduced laterally through the ilium, the SI-Joint, and into the sacrum. This path and resulting placement of the implant structures 20 are best shown in FIGS. 6 and 7A/B. In the illustrated embodiment, three implant structures 20 are placed in this manner. Also in the illustrated embodiment, the implant structures 20 are rectilinear in cross section and triangular in this case, but it should be appreciated that implant structures 20 of other rectilinear cross sections can be used.

Before undertaking a lateral implantation procedure, the physician identifies the SI-Joint segments that are to be fixated or fused (arthrodesed) using, e.g., the Fortin finger test, thigh thrust, FABER, Gaenslen's, compression, distraction, and diagnostic SI joint injection.

Aided by lateral, inlet, and outlet C-arm views, and with the patient lying in a prone position, the physician aligns the greater sciatic notches and then the alae (using lateral visualization) to provide a true lateral position. A 3 cm incision is made starting aligned with the posterior cortex of the sacral canal, followed by blunt tissue separation to the ilium. From the lateral view, the guide pin 38 (with sleeve (not shown)) (e.g., a Steinmann Pin) is started resting on the ilium at a position inferior to the sacrum end plate and just anterior to the sacral canal. In the outlet view, the guide pin 38 should be parallel to the sacrum end plate at a shallow angle anterior (e.g., 15.degree. to 20.degree. off the floor, as FIG. 7A shows). In a lateral view, the guide pin 38 should be posterior to the sacrum anterior wall. In the outlet view, the guide pin 38 should be superior to the first sacral foramen and lateral of mid-line. This corresponds generally to the sequence shown diagrammatically in FIGS. 2A and 2B. A soft tissue protector (not shown) is desirably slipped over the guide pin 38 and firmly against the ilium before removing the guide pin sleeve (not shown).

Over the guide pin 38 (and through the soft tissue protector), the pilot bore 42 is drilled in the manner previously described, as is diagrammatically shown in FIG. 2C. The pilot bore 42 extends through the ilium, through the SI-Joint, and into the S1. The drill bit 40 is removed.

The shaped broach 44 is tapped into the pilot bore 42 over the guide pin 38 (and through the soft tissue protector) to create a broached bore 48 with the desired profile for the implant structure 20, which, in the illustrated embodiment, is triangular. This generally corresponds to the sequence shown diagrammatically in FIG. 2D. The triangular profile of the broached bore 48 is also shown in FIG. 5.

FIGS. 2E and 2F illustrate an embodiment of the assembly of a soft tissue protector or dilator or delivery sleeve 200 with a drill sleeve 202, a guide pin sleeve 204 and a handle 206. In some embodiments, the drill sleeve 202 and guide pin sleeve 204 can be inserted within the soft tissue protector 200 to form a soft tissue protector assembly 210 that can slide over the guide pin 208 until bony contact is achieved. The soft tissue protector 200 can be any one of the soft tissue protectors or dilators or delivery sleeves disclosed herein. In some embodiments, an expandable dilator or delivery sleeve 200 as disclosed herein can be used in place of a conventional soft tissue dilator. In the case of the expandable dilator, in some embodiments, the expandable dilator can be slid over the guide pin and then expanded before the drill sleeve 202 and/or guide pin sleeve 204 are inserted within the expandable dilator. In other embodiments, insertion of the drill sleeve 202 and/or guide pin sleeve 204 within the expandable dilator can be used to expand the expandable dilator.

In some embodiments, a dilator can be used to open a channel though the tissue prior to sliding the soft tissue protector assembly 210 over the guide pin. The dilator(s) can be placed over the guide pin, using for example a plurality of sequentially larger dilators or using an expandable dilator. After the channel has been formed through the tissue, the dilator(s) can be removed and the soft tissue protector assembly can be slid over the guide pin. In some embodiments, the expandable dilator can serve as a soft tissue protector after being expanded. For example, after expansion the drill sleeve and guide pin sleeve can be inserted into the expandable dilator.

As shown in FIGS. 5 and 6, a triangular implant structure 20 can be now tapped through the soft tissue protector over the guide pin 38 through the ilium, across the SI-Joint, and into the sacrum, until the proximal end of the implant structure 20 is flush against the lateral wall of the ilium (see also FIGS. 7A and 7B). The guide pin 38 and soft tissue protector are withdrawn, leaving the implant structure 20 residing in the broached passageway, flush with the lateral wall of the ilium (see FIGS. 7A and 7B). In the illustrated embodiment, two additional implant structures 20 are implanted in this manner, as FIG. 6 best shows. In other embodiments, the proximal ends of the implant structures 20 are left proud of the lateral wall of the ilium, such that they extend 1, 2, 3 or 4 mm outside of the ilium. This ensures that the implants 20 engage the hard cortical portion of the ilium rather than just the softer cancellous portion, through which they might migrate if there was no structural support from hard cortical bone. The hard cortical bone can also bear the loads or forces typically exerted on the bone by the implant 20.

The implant structures 20 are sized according to the local anatomy. For the SI-Joint, representative implant structures 20 can range in size, depending upon the local anatomy, from about 35 mm to about 60 mm in length, and about a 7 mm inscribed diameter (i.e. a triangle having a height of about 10.5 mm and a base of about 12 mm). The morphology of the local structures can be generally understood by medical professionals using textbooks of human skeletal anatomy along with their knowledge of the site and its disease or injury. The physician is also able to ascertain the dimensions of the implant structure 20 based upon prior analysis of the morphology of the targeted bone using, for example, plain film x-ray, fluoroscopic x-ray, or MRI or CT scanning.

Using a lateral approach, one or more implant structures 20 can be individually inserted in a minimally invasive fashion across the SI-Joint, as has been described. Conventional tissue access tools, obturators, cannulas, and/or drills can be used for this purpose. Alternatively, the novel tissue access tools described above and in U.S. Provisional Patent Application No. 61/609,043, titled “TISSUE DILATOR AND PROTECTER” and filed Mar. 9, 2012, which is hereby incorporated by reference in its entirety, can also be used. No joint preparation, removal of cartilage, or scraping are required before formation of the insertion path or insertion of the implant structures 20, so a minimally invasive insertion path sized approximately at or about the maximum outer diameter of the implant structures 20 can be formed.

The implant structures 20 can obviate the need for autologous bone graft material, additional pedicle screws and/or rods, hollow modular anchorage screws, cannulated compression screws, threaded cages within the joint, or fracture fixation screws. Still, in the physician's discretion, bone graft material and other fixation instrumentation can be used in combination with the implant structures 20.

In a representative procedure, one to six, or perhaps up to eight, implant structures 20 can be used, depending on the size of the patient and the size of the implant structures 20. After installation, the patient would be advised to prevent or reduce loading of the SI-Joint while fusion occurs. This could be about a six to twelve week period or more, depending on the health of the patient and his or her adherence to post-op protocol.

The implant structures 20 make possible surgical techniques that are less invasive than traditional open surgery with no extensive soft tissue stripping. The lateral approach to the SI-Joint provides a straightforward surgical approach that complements the minimally invasive surgical techniques. The profile and design of the implant structures 20 minimize or reduce rotation and micromotion. Rigid implant structures 20 made from titanium provide immediate post-op SI Joint stability. A bony in-growth region 24 comprising a porous plasma spray coating with irregular surface supports stable bone fixation/fusion. The implant structures 20 and surgical approaches make possible the placement of larger fusion surface areas designed to maximize post-surgical weight bearing capacity and provide a biomechanically rigorous implant designed specifically to stabilize the heavily loaded SI-Joint.

To improve the stability and weight bearing capacity of the implant, the implant can be inserted across three or more cortical walls. For example, after insertion the implant can traverse two cortical walls of the ilium and at least one cortical wall of the sacrum. The cortical bone is much denser and stronger than cancellous bone and can better withstand the large stresses found in the SI-Joint. By crossing three or more cortical walls, the implant can spread the load across more load bearing structures, thereby reducing the amount of load borne by each structure. In addition, movement of the implant within the bone after implantation is reduced by providing structural support in three locations around the implant versus two locations.

Use of the Implant

The spine (see FIGS. 8A-8C) is a complex interconnecting network of nerves, joints, muscles, tendons and ligaments, and all are capable of producing pain.

The spine is made up of small bones, called vertebrae. The vertebrae protect and support the spinal cord. They also bear the majority of the weight put upon the spine.

Between each vertebra is a soft, gel-like “cushion,” called an intervertebral disc. These flat, round cushions act like shock absorbers by helping absorb pressure and keep the bones from rubbing against each other. The intervertebral disc also binds adjacent vertebrae together. The intervertebral discs are a type of joint in the spine. Intervertebral disc joints can bend and rotate a bit but do not slide as do most body joints.

Each vertebra has two other sets of joints, called facet joints (see FIG. 8B). The facet joints are located at the back of the spine (posterior). There is one facet joint on each lateral side (right and left). One pair of facet joints faces upward (called the superior articular facet) and the other pair of facet joints faces downward (called the inferior articular facet). The inferior and superior facet joints mate, allowing motion (articulation), and link vertebrae together. Facet joints are positioned at each level to provide the needed limits to motion, especially to rotation and to prevent forward slipping (spondylolisthesis) of that vertebra over the one below.

In this way, the spine accommodates the rhythmic motions required by humans to walk, run, swim, and perform other regular movements. The intervertebral discs and facet joints stabilize the segments of the spine while preserving the flexibility needed to turn, look around, and get around.

Degenerative changes in the spine can adversely affect the ability of each spinal segment to bear weight, accommodate movement, and provide support. When one segment deteriorates to the point of instability, it can lead to localized pain and difficulties. Segmental instability allows too much movement between two vertebrae. The excess movement of the vertebrae can cause pinching or irritation of nerve roots. It can also cause too much pressure on the facet joints, leading to inflammation. It can cause muscle spasms as the paraspinal muscles try to stop the spinal segment from moving too much. The instability eventually results in faster degeneration in this area of the spine. Degenerative changes in the spine can also lead to spondylolysis and spondylolisthesis. Spondylolisthesis is the term used to describe when one vertebra slips forward on the one below it. This usually occurs because there is a spondylolysis (defect) in the vertebra on top. For example, a fracture or a degenerative defect in the interarticular parts of lumbar vertebra L1 may cause a forward displacement of the lumbar vertebra L5 relative to the sacral vertebra S1 (called L5-S1 spondylolisthesis). When a spondylolisthesis occurs, the facet joint can no longer hold the vertebra back. The intervertebral disc may slowly stretch under the increased stress and allow other upper vertebra to slide forward.

An untreated persistent, episodic, severely disabling back pain problem can easily ruin the active life of a patient. In many instances, pain medication, splints, or other normally-indicated treatments can be used to relieve intractable pain in a joint. However, in for severe and persistent problems that cannot be managed by these treatment options, degenerative changes in the spine may require a bone fusion surgery to stop both the associated disc and facet joint problems.

A fusion is an operation where two bones, usually separated by a joint, are allowed to grow together into one bone. The medical term for this type of fusion procedure is arthrodesis.

Lumbar fusion procedures have been used in the treatment of pain and the effects of degenerative changes in the lower back. A lumbar fusion is a fusion in the S1-L5-L4 region in the spine.

One conventional way of achieving a lumbar fusion is a procedure called anterior lumbar interbody fusion (ALIF). In this procedure, the surgeon works on the spine from the front (anterior) and removes a spinal disc in the lower (lumbar) spine. The surgeon inserts a bone graft into the space between the two vertebrae where the disc was removed (the interbody space). The goal of the procedure is to stimulate the vertebrae to grow together into one solid bone (known as fusion). Fusion creates a rigid and immovable column of bone in the problem section of the spine. This type of procedure is used to try and reduce back pain and other symptoms.

Facet joint fixation procedures have also been used for the treatment of pain and the effects of degenerative changes in the lower back. These procedures take into account that the facet joint is the only true articulation in the lumbosacral spine. In one conventional procedure for achieving facet joint fixation, the surgeon works on the spine from the back (posterior). The surgeon passes screws from the spinous process through the lamina and across the mid-point of one or more facet joints.

Conventional treatment of spondylolisthesis may include a laminectomy to provide decompression and create more room for the exiting nerve roots. This can be combined with fusion using, e.g., an autologous fibular graft, which may be performed either with or without fixation screws to hold the bone together. In some cases the vertebrae are moved back to the normal position prior to performing the fusion, and in others the vertebrae are fused where they are after the slip, due to the increased risk of injury to the nerve with moving the vertebra back to the normal position.

Currently, these procedures entail invasive open surgical techniques (anterior and/or posterior). Further, ALIF entails the surgical removal of the disc. Like all invasive open surgical procedures, such operations on the spine risk infections and require hospitalization. Invasive open surgical techniques involving the spine continue to be a challenging and difficult area.

A. Use of the Implant Structures to Achieve Anterior Lumbar Interbody Fusion

FIG. 9 shows, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures 20 sized and configured to achieve anterior lumbar interbody fusion, in a non-invasive manner and without removal of the intervertebral disc. FIGS. 10 to 12 show the assembly after implantation, respectively, in an anterior view, a right lateral view, and a superior left lateral perspective view.

In the representative embodiment illustrated in FIGS. 10 to 12, the assembly comprises three implant structures 20. It should be appreciated, however, that a given assembly can include a greater or lesser number of implant structures 20.

In the representative embodiment shown in FIGS. 10 to 12, the three implant structures 20 are spaced in an adjacent lateral array. The implant structures 20 extend from an anterolateral region of a selected vertebral body (i.e., a lateral region anterior to a transverse process), across the intervertebral disc into an opposite anterolateral region of an adjacent caudal (inferior) vertebra. As shown in FIGS. 10 to 12, the array of implant structures 20 extends in an angled path (e.g., about 20° to about 40° off horizontal) through the cranial (superior) lumbar vertebral body (shown as L4) in an inferior direction, through the adjoining intervertebral disc, and terminates in the next adjacent caudal (inferior) lumbar vertebral body (shown as L5).

More particularly, in the representative embodiment shown in FIGS. 9 to 12, the implant structures 20 enter the right anterolateral region of vertebra L4 and terminate within the left anterolateral interior of vertebra L5, spanning the intervertebral disc between L4 and L5.

Alternatively, or in combination, an array of implant structures 20 can likewise extend between L5 and S1 in the same trans-disc formation.

The implant structures 20 are sized according to the local anatomy. The implant structures 20 can be sized differently, e.g., 3 mm, 4 mm, 6 mm, etc.), to accommodate anterolateral variations in the anatomy. The implant structures 20 can be sized for implantation in adults or children.

The intimate contact created between the bony in-growth or through-growth region 24 along the surface of the implant structure 20 accelerates bony in-growth or through-growth onto, into, or through the implant structure 20, to accelerate trans-disc fusion between these lumbar vertebrae.

FIGS. 13A to 13G diagrammatically show, for purposes of illustration, a representative lateral (or posterolateral) procedure for implanting the assembly of implant structures 20 shown in FIGS. 10 to 12.

The physician identifies the vertebrae of the lumbar spine region that are to be fused using, e.g., the Faber Test, or CT-guided injection, or X-ray/MRI of the lumbar spine. Aided by lateral and anterior-posterior (A-P) c-arms, and with the patient lying in a prone position (on their stomach), the physician makes a 3 mm incision laterally or posterolaterally from the side (see FIG. 13A). Aided by conventional visualization techniques, e.g., using X-ray image intensifiers such as a C-arms or fluoroscopes to produce a live image feed which is displayed on a TV screen, a guide pin 38 is introduced by conventional means into L4 (see FIG. 13B) for the first, most anterolateral implant structure (closest to the right transverse process of L4), in the desired angled inferiorly-directed path through the intervertebral disc and into the interior left anterolateral region of vertebra L5.

When the guide pin 38 is placed in the desired orientation, the physician desirable slides a soft tissue protector over the guide pin 38 before proceeding further. To simplify the illustration, the soft tissue protector is not shown in the drawings.

Through the soft tissue protector, a cannulated drill bit 40 is next passed over the guide pin 38 (see FIG. 13C). The cannulated drill bit 40 forms a pilot insertion path or bore 42 along the first angled path defined by the guide pin 38. A single drill bit or multiple drill bits 40 can be employed to drill through bone fragments or bone surfaces to create a pilot bore 42 of the desired size and configuration.

When the pilot bore 42 is completed, the cannulated drill bit 40 is withdrawn over the guide pin 38.

Through the soft tissue protector, a broach 44 having the external geometry and dimensions matching the external geometry and dimensions of the implant structure 20 (which, in the illustrated embodiment, is triangular) (see FIG. 13D) is tapped through the soft tissue protector over the guide pin 38 and into the pilot bore 42. The shaped broach 44 cuts along the edges of the pilot bore 42 to form the desired profile (which, in the illustrated embodiment, is triangular) to accommodate the implant structure 20.

The broach 44 is withdrawn (see FIG. 13E), and the first, most anterolateral implant structure 20 is passed over the guide pin 38 through the soft tissue protector into the broached bore 48. The guide pin 38 and soft tissue protector are withdrawn from the first implant structure 20.

The physician repeats the above-described procedure sequentially for the next anterolateral implant structures 20: for each implant structure, inserting the guide pin 38, forming the pilot bore, forming the broached bore, inserting the respective implant structure, withdrawing the guide pin, and then repeating the procedure for the next implant structure, and so on until all implant structures 20 are placed (as FIGS. 13F and 13G indicate). The incision site(s) are closed.

In summary, the method for implanting the assembly of the implant structures 20 comprises (i) identifying the bone structures to be fused and/or stabilized; (ii) opening an incision; (iii) using a guide pin to established a desired implantation path through bone for the implant structure 20; (iv) guided by the guide pin, increasing the cross section of the path; (v) guided by the guide pin, shaping the cross section of the path to correspond with the cross section of the implant structure 20; (vi) inserting the implant structure 20 through the path over the guide pin; (vii) withdrawing the guide pin; (viii) repeating, as necessary, the procedure sequentially for the next implant structure(s) until all implant structures 20 contemplated are implanted; and (ix) closing the incision.

As FIGS. 14 and 15 show, assemblies comprising one or more implant structures 20 can be inserted from left and/or right anterolateral regions of a given lumbar vertebra, in an angled path through the intervertebral disc and into an opposite anterolateral interior region of the next inferior lumbar vertebra.

For purposes of illustration, FIG. 14 shows two implant structures 20 entering on the right anterolateral side of L4, through the intervertebral disc and into the left anterolateral region of L5, and one implant structure 20 entering on the left anterolateral side of L4, through the intervertebral disc and into the right anterolateral region of L5. In this arrangement, the left and right implant structures 20 cross each other in transit through the intervertebral disc.

As another illustration of a representative embodiment, FIG. 15 shows one implant structure 20 entering on the right anterolateral side of L4, through the intervertebral disc and into the left anterolateral region of L5, and one implant structure 20 entering on the left anterolateral side of L4, through the intervertebral disc and into the right anterolateral region of L5. In this arrangement as well, the left and right implant structures 20 cross each other in transit through the intervertebral disc.

B. Use of Implant Structures to Achieve Translaminal Lumbar Fusion (Posterior Approach)

FIG. 16 shows, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures 20 sized and configured to achieve translaminar lumbar fusion in a non-invasive manner and without removal of the intervertebral disc. FIG. 17 shows the assembly after implantation, respectively, in an inferior transverse plane view.

As can be seen in the representative embodiment illustrated in FIGS. 16 and 17, the assembly comprises two implant structures 20. The first implant structure 20 extends from the left superior articular process of vertebra L5, through the adjoining facet capsule into the left inferior articular process of vertebra L4, and, from there, further through the lamina of vertebra L4 into an interior right posterolateral region of vertebra L4 adjacent the spinous process. The second implant structure 20 extends from the right superior articular process of vertebra L5, through the adjoining facet capsule into the right inferior articular process of vertebra L4, and, from there, further through the lamina of vertebra L4 into an interior left posterolateral region of vertebra L4 adjacent the spinous process. The first and second implant structures 20 cross each other within the medial lamina of vertebra L4.

The first and second implant structures 20 are sized and configured according to the local anatomy. The selection of a translaminar lumbar fusion (posterior approach) is indicated when the facet joints are aligned with the sagittal plane. Removal of the intervertebral disc is not required, unless the condition of the disc warrants its removal.

A procedure incorporating the technical features of the procedure shown in FIGS. 13A to 13G can be tailored to a posterior procedure for implanting the assembly of implant structures 20 shown in FIGS. 16 and 17. The method comprises (i) identifying the vertebrae of the lumbar spine region that are to be fused; (ii) opening an incision, which comprises, e.g., with the patient lying in a prone position (on their stomach), making a 3 mm posterior incision; and (iii) using a guide pin to established a desired implantation path through bone for the first (e.g., left side) implant structure 20, which, in FIGS. 16 and 17, traverses through the left superior articular process of vertebra L5, through the adjoining facet capsule into the left inferior articular process of vertebra L4, and then through the lamina of vertebra L4 into an interior right posterolateral region of vertebra L4 adjacent the spinous process. The method further includes (iv) guided by the guide pin, increasing the cross section of the path; (v) guided by the guide pin, shaping the cross section of the path to correspond with the cross section of the implant structure; (vi) inserting the implant structure 20 through the path over the guide pin; (vii) withdrawing the guide pin; and (viii) using a guide pin to established a desired implantation path through bone for the second (e.g., right side) implant structure 20, which, in FIGS. 16 and 17, traverses through the right superior articular process of vertebra L5, through the adjoining facet capsule into the right inferior articular process of vertebra L4, and through the lamina of vertebra L4 into an interior left posterolateral region of vertebra L4 adjacent the spinous process. The physician repeats the remainder of the above-described procedure sequentially for the right implant structure 20 as for the left, and, after withdrawing the guide pin, closes the incision.

The intimate contact created between the bony in-growth or through-growth region 24 along the surface of the implant structure 20 across the facet joint accelerates bony in-growth or through-growth onto, into, or through the implant structure 20, to accelerate fusion of the facets joints between L4 and L5. Of course, translaminar lumbar fusion between L5 and S1 can be achieved using first and second implant structures in the same manner.

C. Use of Implant Structures to Achieve Lumbar Facet Fusion (Posterior Approach)

FIG. 18 shows, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures 20 sized and configured to lumbar facet fusion, in a non-invasive manner and without removal of the intervertebral disc. FIGS. 19 and 20 show the assembly after implantation, respectively, in an inferior transverse plane view and a lateral view.

As can be seen in the representative embodiment illustrated in FIGS. 18 and 20, the assembly comprises two implant structures 20. The first implant structure 20 extends from the left inferior articular process of vertebra L4, through the adjoining facet capsule into the left superior articular process of vertebra L5 and into the pedicle of vertebra L5. The second implant structure 20 extends from the right inferior articular process of vertebra L5, through the adjoining facet capsule into the right superior articular process of vertebra L5 and into the pedicle of vertebra L5. In this arrangement, the first and second implant structures 20 extend in parallel directions on the left and right pedicles of vertebra L5. The first and second implant structures 20 are sized and configured according to the local anatomy. The selection of lumbar facet fusion (posterior approach) is indicated when the facet joints are coronally angled. Removal of the intervertebral disc is not necessary, unless the condition of the disc warrants its removal.

A procedure incorporating the technical features of the procedure shown in FIGS. 13A to 13G can be tailored to a posterior procedure for implanting the assembly of implant structures 20 shown in FIGS. 18 to 20. The method comprises (i) identifying the vertebrae of the lumbar spine region that are to be fused; (ii) opening an incision, which comprises, e.g., with the patient lying in a prone position (on their stomach), making a 3 mm posterior incision; and (iii) using a guide pin to established a desired implantation path through bone for the first (e.g., left side) implant structure 20, which, in FIGS. 18 to 20, traverses through the left inferior articular process of vertebra L4, through the adjoining facet capsule into the left superior articular process of vertebra L5 and into the pedicle of vertebra L5. The method further includes (iv) guided by the guide pin, increasing the cross section of the path; (v) guided by the guide pin, shaping the cross section of the path to correspond with the cross section of the implant structure 20; (vi) inserting the implant structure 20 through the path over the guide pin; (vii) withdrawing the guide pin; and (viii) using a guide pin to established a desired implantation path through bone for the second (e.g., right side) implant structure 20, which, in FIGS. 18 to 20, traverses through the right inferior articular process of vertebra L5, through the adjoining facet capsule into the right superior articular process of vertebra L5 and into the pedicle of vertebra L5. The physician repeats the remainder of the above-described procedure sequentially for the right implant structure 20 as for the left and, withdrawing the guide pin, closes the incision.

The intimate contact created between the bony in-growth or through-growth region 24 along the surface of the implant structure 20 across the facet joint accelerates bony in-growth or through-growth onto, into, or through the implant structure 20, to accelerate fusion of the facets joints between L4 and L5.

Of course, translaminar lumbar fusion between L5 and S1 can be achieved using first and second implant structures in the same manner.

D. Use of Implant Structures to Achieve Trans-Iliac Lumbar Fusion (Anterior Approach)

FIG. 21A shows, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures 20 sized and configured to achieve fusion between lumbar vertebra L5 and sacral vertebra S1, in a non-invasive manner and without removal of the intervertebral disc. FIG. 21B shows the assembly after implantation.

In the representative embodiment illustrated in FIGS. 21A and 21B, the assembly comprises two implant structures 20. It should be appreciated, however, that a given assembly can include a greater or lesser number of implant structures 20.

As FIGS. 21A and 21B show, the assembly comprises two implant structures 20 inserted from left and right anterolateral regions of lumbar vertebra L5, in an angled path (e.g., about 20.degree. to about 40.degree. off horizontal) through the intervertebral disc in an inferior direction, into and through opposite anterolateral interior regions of sacral vertebra S1, through the sacro-iliac joint, and terminating in the ilium. In this arrangement, the left and right implant structures 20 cross each other in transit through the intervertebral disc. As before described, the implant structures 20 are sized according to the local anatomy.

The intimate contact created between the bony in-growth or through-growth region 24 along the surface of the implant structure 20 accelerates bony in-growth or through-growth onto, into, or through the implant structure 20, to accelerate lumbar trans-iliac fusion between vertebra L5 and S1.

A physician can employ the lateral (or posterolateral) procedure as generally shown in FIGS. 13A to 13G for implanting the assembly of implant structures 20 shown in FIGS. 21A and 21B, including forming a pilot bore over a guide pin inserted in the angled path, forming a broached bore, inserting the right implant 20 structure, withdrawing the guide pin, and repeating for the left implant structure 20, or vice versa. The incision site(s) are closed.

The assembly as described makes possible the achievement of trans-iliac lumbar fusion using an anterior in a non-invasive manner, with minimal incision, and without necessarily removing the intervertebral disc between L5 and S1.

E. Use of Implant Structures to Achieve Trans-Iliac Lumbar Fusion (Postero-Lateral Approach from Posterior Iliac Spine)

FIG. 22A shows, in an exploded view prior to implantation, another representative configuration of an assembly of one or more implant structures 20 sized and configured to achieve fusion between lumbar vertebra L5 and sacral vertebra S1, in a non-invasive manner and without removal of the intervertebral disc. FIGS. 22B and 22C show the assembly after implantation.

As FIGS. 22A and 22B show, the one or more implant structures are introduced in a postero-lateral approach entering from the posterior iliac spine of the ilium, angling through the SI-Joint into and through the sacral vertebra S1, and terminating in the lumbar vertebra L5. This path and resulting placement of the implant structures 20 are also shown in FIG. 22C. In the illustrated embodiment, two implant structures 20 are placed in this manner, but there can be more or fewer implant structures 20. Also in the illustrated embodiment, the implant structures 20 are triangular in cross section, but it should be appreciated that implant structures 20 of other cross sections as previously described can be used.

The postero-lateral approach involves less soft tissue disruption that the lateral approach, because there is less soft tissue overlying the entry point of the posterior iliac spine of the ilium. Introduction of the implant structure 20 from this region therefore makes possible a smaller, more mobile incision.

The set-up for a postero-lateral approach is generally the same as for a lateral approach. It desirably involves the identification of the lumbar region that is to be fixated or fused (arthrodesed) using, e.g., the Faber Test, or CT-guided injection, or X-ray/MRI of SI Joint. It is desirable performed with the patient lying in a prone position (on their stomach) and is aided by lateral and anterior-posterior (A-P) c-arms. The same surgical tools are used to form the pilot bore over a guide pin (e.g., on the right side), except the path of the pilot bore now starts from the posterior iliac spine of the ilium, angles through the SI-Joint, and terminates in the lumbar vertebra L5. The broached bore is formed, and the right implant 20 structure is inserted. The guide pin is withdrawn, and the procedure is repeated for the left implant structure 20, or vice versa. The incision site(s) are closed.

The assembly as described makes possible the achievement of trans-iliac lumbar fusion using a postero-lateral approach in a non-invasive manner, with minimal incision, and without necessarily removing the intervertebral disc between L5 and S1.

F. Use of Implant Structures to Stabilize a Spondylolisthesis

FIG. 23 shows a spondylolisthesis at the L5/S1 articulation, in which the lumbar vertebra L5 is displaced forward (anterior) of the sacral vertebra S1. As FIG. 23 shows, the posterior fragment of L5 remains in normal relation to the sacrum, but the anterior fragment and the L5 vertebral body has moved anteriorly. Spondylolisthesis at the L5/S1 articulation can result in pressure in the spinal nerves of the cauda equine as they pass into the superior part of the sacrum, causing back and lower limb pain.

FIG. 24A shows, in an exploded view prior to implantation, a representative configuration of an assembly of one or more implant structures 20 sized and configured to stabilize the spondylolisthesis at the L5/S1 articulation. FIGS. 24B and 24C show the assembly after implantation.

As shown, the implant structure 20 extends from a posterolateral region of the sacral vertebra S1, across the intervertebral disc into an opposite anterolateral region of the lumbar vertebra L5. The implant structure 20 extends in an angled path (e.g., about 20.degree. to about 40.degree. off horizontal) through the sacral vertebra S1 in a superior direction, through the adjoining intervertebral disc, and terminates in the lumbar vertebra L5.

A physician can employ a posterior approach for implanting the implant structure 20 shown in FIGS. 24A, 24B, and 24C, which includes forming a pilot bore over a guide pin inserted in the angled path from the posterior of the sacral vertebra S1 through the intervertebral disc and into an opposite anterolateral region of the lumbar vertebra L5, forming a broached bore, inserting the implant structure 20, and withdrawing the guide pin. The incision site is then closed. As previously described, more than one implant structure 20 can be placed in the same manner to stabilize a spondylolisthesis. Furthermore, a physician can fixate the implant structure(s) 20 using the anterior trans-iliac lumbar path, as shown in FIG. 21A/B or 22A/B/C.

The physician can, if desired, combine stabilization of the spondylolisthesis, as shown in FIG. 24A/B/C, with a reduction, realigning L5 and S-1. The physician can also, if desired, combine stabilization of the spondylolisthesis, as shown in FIG. 24A/B/C (with or without reduction of the spondylolisthesis), with a lumbar facet fusion, as shown in FIGS. 18 to 20. The physician can also, if desired, combine stabilization of the spondylolisthesis, as shown in FIG. 24A/B/C, with a decompression, e.g., by the posterior removal of the spinous process and laminae bilaterally.

Neuromonitoring Systems and Methods

To reduce the likelihood of damaging or impinging upon a nerve during the implantation procedure, a neuromonitoring system can be used to detect the location of neural tissues proximate the implantation site.

A. Guide Pin Adaptor

In some embodiments as illustrated in FIG. 25A, a neuromonitoring adaptor 2500 can be used to covert a guide pin 38 to a neuromonitoring probe 2502. The adaptor 2500 can be attached or otherwise electrically coupled to the proximal end of a metal electrically conductive guide pin 38. In some embodiments, the adaptor 2500 can have a receptacle 2504 for receiving the proximal end of the guide pin 38. In other embodiments, the adaptor 2500 can be a collar that wraps around a proximal portion of the guide pin, or a clip that can be fastened to the proximal end or portion of the guide pin.

In some embodiments, as illustrated in FIG. 25A, a non-conductive guide pin sleeve 204 can be disposed over the guide pin 38 to insulate and shield the body of the guide pin 38 from receiving electrical signals from the body when the neuromonitoring probe is used to sense or detect electrical signals generated by the patient's body, while leaving the distal tip of the guide pin 38 exposed. In addition, the insulating sleeve 204 shields the body of the guide pin 38 from delivering electrical energy to the patient's body when the neuromonitoring probe 2502 is used to deliver electrical stimuli to the body. By shielding the body of the guide pin 38, the electrical stimulus is delivered through the tip of the guide pin which allows the delivery the electrical stimulus to be localized to the tip. The sleeve 204 can be made of a non-conductive electrically insulating material, such as plastic, rubber, silicone, and the like.

The adaptor 2500 can also be electrically connected, by a wire 2506 for example, to a computing device 2508 and/or signal generator 2509 that is programmed and configured to generate the electrical stimulus and/or to receive and process the electrical signals detected by the neuromonitoring probe 2502. As shown in FIG. 25B, in some embodiments, the receptacle 2504 of the adaptor 2500 can have one or more metal leaf springs 2510 that hold the guide pin 38 within the receptacle while also forming an electrical contact with the guide pin 38. In other embodiments, instead of a leaf spring, the adaptor 2500 can have one or more electrical brushes 2511 to form an electrical contact with the guide pin. The electrical brushes can be made of graphite, metal, and other types of suitable conductive materials. In other embodiments as shown in FIG. 25D, the receptacle 2504 can have one or more metal ball plungers 2512 or spring pins that serve to secure a guide pin 38 having a corresponding groove 2514 or recess located on the proximal end of the guide pin 38. The ball plunger 2512 or spring pin also can form an electrical contact with the guide pin 38.

As mentioned above, the adaptor can be a collar 2516, as shown in FIG. 25E. In some embodiments, the collar 2516 can one or more ball plungers 2518 that can secure the collar 2516 to the guide pin while also providing an electrical contact with the guide pin. In another embodiment, the adaptor can be a clip 2520 or clasp as illustrated in FIG. 25F. The clip 2520 can have a pair of arcuate arms 2522 that rotate around a pivot 2524. A spring around the pivot 2524 can bias the arms 2522 to a closed configuration that allows the clip to securely grip the guide pin 38. The arms 2522 can be opened by squeezing together a pair of handles 2526 attached to the arms 2522. The collar 2516 and/or clip 2520 can be used with a guide pin 38 with or without a groove on the proximal end.

FIGS. 25G and 25H illustrate another embodiment of a guide pin adaptor 2530 that can be placed over a guide pin like a cap. The guide pin adaptor 2530 can have cap body 2532 with a receptacle 2534 sized and shaped to receive the guide pin. An electrical contact 2536, which can be made of metal or another conductive material for example, can be disposed within the receptacle to make electrical contact with the guide pin. A wire 2538, which is in electrical communication with the electrical contact 2536, can extend from the cap body 2532 and terminate in a wire connector 2540, which can be connected to an electrical jack or outlet, for example. The wire connector 2540 can have a strain relief portion 2544 with alternating cutouts that provide the strain relief portion with increased flexibility wherein the wire 2538 connects with the wire connector 2540. The cap body 2532 can have a flange 2542 located on the proximal end of the cap body 2532 that provides the user a part to grip when putting on or removing the adaptor.

FIG. 25I illustrates another example of a guide pin adaptor 2550 that can be clipped onto a guide pin. The guide pin adaptor 2550 can have a clip portion 2552 that has a lower jaw 2554 and an upper jaw 2556. Each jaw portion can have an electrically conductive inner portion that can grip the guide pin, and an insulating cover portion that can be handled by the user. The two jaw portions can pivot about an axis and can be tensioned by a spring or other mechanism to be biased to a closed position. The clip portion 2552 can be similar to an alligator clip, for example. A wire 2558 can extend from the clip portion 2552 and can terminate in a wire connector 2560, which can be connected to an electrical jack or outlet, for example.

Returning to FIG. 25A, the signal generator 2509 can deliver electrical stimuli at regular intervals, or in an on-demand manner with a push of a button, which can be located on the adaptor 2500, the signal generator, or the computing device 2508. In some embodiments, the signal generator can be integrated with the computing device 2508, while in other embodiments, the signal generator can be a separate device that is connected to the guide pin 38 and optionally also the computing device. In other embodiments, the adaptor 2500 can include a wireless transmitter, such as a Bluetooth or WiFi transmitter.

The computing device 2508 can have a display 2510 and input/output features, such as a keyboard or touchscreen display for entering input. The computing device 2508 can also be in communication with one or more recording electrodes 2501 that be placed subcutaneously or intramuscularly at various sites downstream of nerves located at the operating site. The computing device 2508 can process and display the electrophysiological signals detected by the recording electrodes 2501.

B. Modified Guide Pin Cannula

FIG. 26A illustrates an embodiment of a modified guide pin cannula 2600. The guide pin cannula 2600 has a lumen 2602 for receiving a guide pin and one or more internal conductive contacts 2604 disposed on the lumen wall that can electrically couple the guide pin with a signal generator and/or computing device for monitoring and processing the signals received by electrodes placed on the patient's body. The elongate shaft portion of the guide pin cannula 2600 can be made of a nonconductive material such as a plastic, or it can have a nonconductive coating applied to its outer and/or inner surface. This allows a guide pin inserted through the modified guide pin cannula 2600 to deliver a localized electrical stimulus through the tip of the guide pin and not inadvertently through the guide pin cannula to the tissues surrounding the guide pin cannula 2600. In some embodiments, the internal conductive contacts 2604 can be leaf spring type contacts that can function to provide an electrical contact with the guide pin and optionally to hold the guide pin in place within the guide pin cannula 2600. In other embodiments, the internal conductive contacts 2604 can a ball plunger or spring pin type contact.

FIG. 26B illustrates another embodiment of a modified guide pin cannula 2600′ that utilizes a conductive contact insert 2604′ that can be removably or permanently disposed in the lumen 2602′ of the guide pin cannula 2600′. For example, the conductive contact insert 2604′ can be inserted into the proximal end of the lumen 2602′ to electrically couple the guide pin with the signal generator and/or computing device. The conductive contact insert 2604′ can have electrical contacts 2606′, such as leaf spring contacts, disposed within the guide pin cannula lumen 2602′ that engage the guide pin when it is inserted into the guide pin cannula lumen 2602′. In some embodiments, the elongate body 2608′ of the guide pin cannula 2600′ can be made of a nonconductive material, such as plastic, or it can be coated with a nonconductive material so that it does not interfere with electrical signals or stimuli sensed or delivered by the guide pin.

FIG. 26C illustrates another embodiment of a modified guide pin cannula 2600″, similar to that shown in FIG. 26B, but with an additional insulating sheath 2610″ disposed within the lumen 2602″ of the guide pin cannula 2600″. The sheath 2610″ can be used to shield an electrically conductive guide pin cannula 2600″ from the conductive contact insert 2604″. The conductive contact insert 2604″ can be disposed within the guide pin cannula lumen 2602″ and insulating sheath 2610″. When the guide pin is inserted into the guide pin cannula lumen 2602″, it contacts the electrical contacts 2606″ of the conductive contact insert 2604 and the insulating sheath 2610″.

FIG. 26D illustrates a guide pin cannula 2600′ with a different conductive contact 2604′″ configuration. Instead of placing the conductive contact 2604′″ within the lumen 2602′″ of the guide pin cannula 2600′″, the conductive contact 2604′″ can be placed on the proximal end of the guide pin cannula 2600′″ such that the conductive contact 2604′″ extends proximally from the proximal end of the guide pin cannula 2600′″. The conductive contact 2604′″ can be biased towards the longitudinal axis of the guide pin cannula 2600′″ in order to ensure contact with the guide pin.

C. Modified Impactor

The above embodiments describe ways to detect nerve location using the guide pin, which allows the operator to avoid nerve impingement. However, the implant may have a substantially larger cross-sectional area than the guide pin, and therefore, the implant may displace additional tissue over that of the guide pin. Therefore, after the guide pin has been inserted, it can also be desirable to detect whether the implant will impinge or impact neural tissues as the implant is inserted into the patient's body over the guide pin.

In some embodiments as illustrated in FIG. 27A, a guide pin 2700 can be inserted into the patient's body as described herein. For example, the guide pin 2700 can be a standard guide pin or a guide pin with an adaptor to convert the guide pin to a neuromonitoring probe. In addition as described herein, a drill and broach and a variety of sleeves can be used to form a bore around the guide pin 2700.

In some embodiments, the implant 20 itself can be converted to a neuromonitoring probe by using a modified impactor 2702 to advance the implant 20 into the bore. The modified impactor 2702 can have one or more electrical contacts 2704 located on the distal end of the impactor 2702 that contact the proximal end of the implant 20 during the impaction process. In some embodiments, the impactor 2702 can have an insulated tip 2706 with the electrical contacts 2704. In some embodiments, the insulated tip 2706 is integrated into the impactor 2702, while in other embodiments, the insulated tip 2706 is an adaptor that can be attached to the distal end of a standard impactor to convert a standard impactor into a modified neuromonitoring impactor. The insulated tip 2706 can be made of an electrically nonconductive material, such as plastic. The electrical contacts 2704 can be in electrical communication with a signal generator and/or computing device to turn implant 20 and modified impactor 2702 combination into a neuromonitoring probe. For example, in some embodiments, wires can be used connect the electrical contacts 2704 with the signal generator and/or computing device. The wires can extend proximally from the electrical contacts 2704 through the interior of the impactor 2702 to a proximal portion of the impactor, such as the distal end of the impactor. The wires in the proximal portion of the impactor can terminate in an electrical connector, such as an electrical socket or plug that can be removably connected to a wire from the signal generator and/or computing device.

The tissue protector 2708, through which the guide pin 2700, implant 20 and impactor 2702 are inserted, can be electrically insulated or be made of a nonconductive material. For example, the tissue protector 2708 can have an inner surface that is coated or covered with a nonconductive material, such as plastic. In some embodiments, the outer surface of the tissue protector 2708 can be insulated in addition or instead of the inner surface. When electricity is delivered through the electrical contacts 2704 to the implant 20 to turn the implant into an electrical probe, the insulation functions to isolate the electricity to the implant 20, and optionally the guide pin unless an insulated guide pin is used, and prevents the tissue protector 2708 from becoming electrified. An electrified tissue protector 2708 may deliver unwanted electrical stimulation to various non-target tissues, such as muscle tissue surrounding the tissue protector.

D. Modified Soft Tissue Protector

FIGS. 28A and 28B illustrate an embodiment of a modified tissue protector 2800 that also can convert the implant 20 into a neuromonitoring probe. An insulated wire 2802 can extend proximally from the distal end of the tissue protector 2800 to a proximal portion and/or the proximal end of the tissue protector. The wire 2802 can terminate in a conductive contact 2804 that can be in electrical communication with a signal generator and/or computing device, or can extend proximally past the proximal end of the tissue protector to connect to the signal generator and/or computing device. The conductive contact 2804 can extend past the distal end of the tissue protector 2800 and can be biased inwards towards the interior of the soft tissue protector in order to ensure contact with the implant 20 when the implant is advanced past the distal end of the tissue protector.

In some embodiments, the wire 2802 can be disposed in a channel or tube that runs along the exterior of the soft tissue protector 2800 from the distal end to the proximal end of the tissue protector. In some embodiments, the channel can be integrated into the tissue protector walls.

In some embodiments, the wire 2802 can be attached to a stabilizing pin that is disposed in the tube or channel of the tissue protector. The wire 2802 can be attached to either the distal end or the proximal end of the stabilizing pin. In some embodiments, a clip or collar can be used to removably fasten the wire 2802 to the stabilizing pin.

As described above, the implant 20 can be advanced over an insulated guide pin 2806 in order to isolate the electrical signal to the implant, if desired. In some embodiments, a non-insulated or partially insulated guide pin can be used instead to deliver and/or receive electrical signals from both the guide pin 2806 and implant 20.

FIG. 28C illustrates another embodiment of a modified soft tissue protector 2800′ with one or more conductive contacts 2804′ disposed on the inner surface and distal portion of the soft tissue protector 2800′. The conductive contacts 2804′ can be electrically connected to the signal generator and/or computing device using a wire, which can be insulated, that extends proximally from the conductive contacts 2804′. In some embodiments, the wire can terminate in an electrical port on the proximal end of the soft tissue protector 2800′. In some embodiments, as shown in FIG. 28D, the conductive contacts 2804′ can be added to a standard soft tissue protector using a sleeve adaptor 2810′ that can be fitted over the distal end of the soft tissue protector 2800′. The sleeve adaptor 2810′ can have one or more conductive contacts 2804′ positioned on the inner surface of the sleeve adaptor 2810′ to face the lumen of the soft tissue protector. A wire 2812′ can extend from the sleeve adaptor 2810 to electrically connect the conductive contacts 2804′ to a signal generator and/or computing device.

E. Modified Drill Sleeves

It may also be desirable to also perform neuromonitoring during the drilling of the bore over the guide pin, or during drilling of a bore without the use of a guide pin. In some embodiments, the drill sleeve essentially takes the same or similar form as the guide pin sleeves described with respect to FIGS. 26A-26C, except with a larger lumen for received the drill bit. The drill sleeve can have one or more electrical contacts disposed within the drill sleeve lumen for making electrical contact with the drill bit as it passes through the drill sleeve lumen. For example, the electrical contact can be an electrical brush made of a conductive material like graphite or metal. This electrically couples the drill bit with a signal generator and/or computing device, thereby converting the drill bit into a neuromonitoring probe. As shown in FIG. 29, the drill bit 2900 can have a proximal end for insertion into the drill chuck that is coated or covered with an electrically insulating material 2902. The electrical insulation protects the drill from receiving electricity from the drill bit.

F. Modified Broach

It may also be desirable to perform neuromonitoring during the shaping of the bore with a broach. If a modified soft tissue protector, as described above with respect to FIGS. 28A-28D, is used, a standard broach may be used and converted, like the implant, into a neuromonitoring probe when it is inserted through the modified soft tissue protector.

Alternatively, as shown in FIG. 30, a modified broach 3000 that can be electrically connected to a signal generator and/or computing device so that the broach can function as a neuromonitoring probe. An electrical port 3002 and/or wire 3004 can be located on the proximal end of the broach 3000, but away from the proximal striking surface 3006 of the broach 3000. An insulating sleeve 3008 can also be disposed around the shaft of the broach.

In other embodiments, an adaptor, similar in concept to the guide pin adaptors described above with respect to FIGS. 25A-25E, can be attached to a broach to convert a standard type broach into a neuromonitoring probe.

G. Implant Checking Device

Another way of using the implant as a neuromonitoring probe to check whether the implant is close to a nerve is to use an implant checking device 3100, as shown in FIG. 31A. The implant checking device 3100 can have an elongate body 3102 with an extendable and retractable probe 3104 disposed within a lumen of the elongate body. The probe 3104 can extend from the distal end of the elongate body 3102 to reach a middle portion of the implant to be checked. When extended, the probe 3104 can be biased away from the longitudinal axis L of the implant checking device 3100 so that the probe 3104 will contact the lumen wall of the implant when the probe 3104 is extended into the lumen of the implant. The distal end of the probe 3104 can be ball or curved surface that can slide against the implant. The probe 3104 can be made of an electrically conductive material and can be in electrical communication with a signal generator and/or computing device via a wire 3106 connected to the proximal end of the probe 3104, when the probe 3104 extends entirely through the elongate body. The elongate body 3102 can be a tube made of an electrically insulating material. The elongate body 3102 can also have a tapered distal end to help guide the checking device 3100 into the lumen of the implant, and a spring 3110 can be used to facilitate the extension and retraction of the probe 3104.

In some embodiments, the probe 3104 does not extend entirely through the elongate body, and a pusher 3108 can extend into the proximal end of the elongate body to push the probe 3104 out to its extended configuration. In this embodiment, the wire 3106 can be attached instead to the pusher 3108.

To use the implant checking device 3100, the impactor can be removed from the soft tissue protector and the implant checking device 3100 can be inserted into the soft tissue protector in its place until the tapered distal end of the elongate body 3102 is aligned with the lumen of the implant. Then, the probe 3104 can be extended into the lumen of the implant to make contact with the lumen wall in the middle portion of the implant. An electrical signal can be delivered through the implant checking device to the implant in order to determine whether a nerve is near the implant. The checking procedure can be periodically repeated as the implant is advanced.

FIG. 31B illustrates another embodiment of an implant checking device 3120 with an elongate handle 3122 and a probe 3124, which can be made of a conductive material like metal. The probe 3124 can have a rod portion that extends from the distal end of the handle and a ball portion 3126 at the distal end of the rod. A wire 3128 in electrical communication with the probe 3124 can extend from the proximal end of the rod and can terminate in a wire connector 3130 that can be electrically connected to an electrical jack or outlet, for example. The rod can be a fixed length in some embodiments, while in other embodiments the rod can telescope out to various lengths. In some embodiments, the rod can be straight, while in other embodiments, the distal portion of the rod can be curved.

H. Method of Using Neuromonitoring Equipment During Implantation Procedure

The neuromonitoring devices and systems described above can be used to reduce the likelihood of damaging or impinging upon a nerve during the implantation procedure. In some embodiments, the neuromonitoring system includes one or more neuromonitoring probes, such as those described herein, to deliver an electrical signal at the operating site to stimulate any nerve tissues at or near the operating site. Recording electrodes can be placed at various sites downstream of the nerves located at the operating site, including muscle groups that are stimulated by nerves, directly or indirectly, around the operating site, such as the calf, hamstring, quadriceps, and sphincter, as shown in FIGS. 32A-32C. The recording electrodes can be set to continuously record electrophysiological signals. If nerves are stimulated at the operating site, then one or more of the muscle groups will be stimulated by nerves innervating those muscle groups. The electrodes placed at those muscle groups can detect electrophysiological signals cause by stimulation of nerves at the operating site. Stimulation of nerves at the operating site can occur from physical impingement of the nerves by surgical tools or the implant, or can be the result of delivering an electrical stimulus with a neuromonitoring probe near a nerve at the operating site.

A signal generator can be used to deliver an electrical stimulus through a neuromonitoring probe to the operating site. The electrical stimulus can be delivered periodically and/or in an on-demand manner. The amplitude of the electrical stimulus can range from 1 mA to 30 mA, or 5 mA to 20 mA. The recording electrodes can be in communication with a computing device that can process and display electrophysiological signals detected by the recording electrodes. If one or more of the recording electrodes detect a signal after a 5 mA stimulus is delivered, it may mean that the neuromonitoring probe is near or contacting a nerve at the operating site. In some embodiments, a range between about 1-10 mA can signify that the probe is near or contacting a nerve. The position of the probe can be adjusted, by for example retracting the probe, and another electrical stimulus can be delivered to determine whether the probe is still close to the nerve. If the nerve is stimulated only at 20 mA, it may mean that the nerve is still far enough away that the current position of the instruments and/or implant is safe. In some embodiments, a range between about 10-30 mA can signify that the probe is a safe distance away from any nerves. This can be used to safely position the guide pin, drill, broach, and implant. If the recording electrodes detect a signal, the instruments and/or implant can be retracted, and if necessary or desired, repositioned. In some embodiments, the computing device can generate an audible and/or visible alarm when it detects an electrophysiological signal from one or more recording electrodes that indicates that the neuromonitoring probe is near a nerve or neural tissue. For example, detection of an electrophysiological signal in the absence of the delivery of an electrical stimulus may indicate that physical impingement of a nerve may have occurred, and therefore, an alarm can be generated. In addition, detection of an electrophysiological signal within a predetermined window after delivering a low level electrical stimulus, i.e. 1-10 mA, or less than 5 mA, can indicate that the neuromonitoring probe is close to a nerve or neural tissue, and therefore, an alarm can be generated.

It is understood that this disclosure, in many respects, is only illustrative of the numerous alternative device embodiments of the present invention. Changes may be made in the details, particularly in matters of shape, size, material and arrangement of various device components without exceeding the scope of the various embodiments of the invention. Those skilled in the art will appreciate that the exemplary embodiments and descriptions thereof are merely illustrative of the invention as a whole. While several principles of the invention are made clear in the exemplary embodiments described above, those skilled in the art will appreciate that modifications of the structure, arrangement, proportions, elements, materials and methods of use, may be utilized in the practice of the invention, and otherwise, which are particularly adapted to specific environments and operative requirements without departing from the scope of the invention. In addition, while certain features and elements have been described in connection with particular embodiments, those skilled in the art will appreciate that those features and elements can be combined with the other embodiments disclosed herein. 

What is claimed is:
 1. A method of inserting an implant into a patient, the method comprising: inserting a guide pin into the patient at a first site; delivering a first electrical stimulus through the guide pin while the guide pin is inserted into the patient at the first site; monitoring a second site for a first electrophysiological signal after the step of delivering the first electrical stimulus; drilling a bore over the guide pin at the first site with a drill bit; shaping the bore with a broach; and inserting the implant into the bore.
 2. The method of claim 1, further comprising: delivering a second electrical stimulus through the drill bit; and monitoring the second site for a second electrophysiological signal after the step of delivering the second electrical stimulus.
 3. The method of claim 1, further comprising: delivering a second electrical stimulus through the broach; and monitoring the second site for a second electrophysiological signal after the step of delivering the second electrical stimulus.
 4. The method of claim 1, further comprising: delivering a second electrical stimulus through the implant; and monitoring the second site for a second electrophysiological signal after the step of delivering the second electrical stimulus. 